Ventilation Design Flashcards

According to ASHRAE 62.1, what is the minimum outdoor air ventilation rate for an office space occupied at 5 people per 1,000 sq ft?

Answer: 10 cfm per person

ASHRAE 62.1 specifies 10 cfm per person as the minimum outdoor air rate for office occupancies under standard conditions.

What does the term 'ventilation effectiveness' describe in HVAC design?

Answer: How efficiently outdoor air reaches the breathing zone

Ventilation effectiveness (Ev) measures how well the outdoor air delivered to a space actually reaches the occupants' breathing zone.

A demand-controlled ventilation (DCV) system uses which sensor to modulate outdoor air intake?

Answer: CO2 sensor

DCV systems use CO2 sensors as a proxy for occupancy level to dynamically adjust outdoor air supply and reduce energy waste.

What is the primary purpose of an energy recovery ventilator (ERV) compared to a heat recovery ventilator (HRV)?

Answer: ERV recovers both heat and moisture; HRV recovers heat only

An ERV transfers both sensible heat and latent moisture between exhaust and supply airstreams, while an HRV transfers sensible heat only.

Which ventilation strategy introduces 100% outdoor air and exhausts 100% of return air, with no recirculation?

Answer: Once-through system

A once-through (100% OA) system uses no return air recirculation, making it ideal for spaces like laboratories and hospitals with contamination concerns.

In a multi-zone VAV system, the 'critical zone' is defined as the zone that:

Answer: Requires the highest fraction of outdoor air relative to supply air

The critical zone is the zone with the highest outdoor air fraction (Zp), which drives the system-level outdoor air correction calculation.

What ventilation design approach is most appropriate for a commercial kitchen exhaust hood?

Answer: Local exhaust ventilation

Local exhaust ventilation captures contaminants (grease, heat, combustion gases) at the source before they can disperse into the occupied space.